Alessandro Grippo, Ph.D. A few examples of Sedimentary Structures   Sedimentary structures Last Updated  •  March 3, 2014     HORIZONTAL BEDDING Horizontal Bedding alternating shales and sandstones (trees for scale) © Alessandro Grippo Cedar Breaks National Monument Utah, USA Horizontal Bedding alternating shales and sandstones © Alessandro Grippo Capitol Reef National Park Fruita, Utah, USA Horizontal Bedding in fresh sediment (mature, quartz beach sands) (footprints for scale) © Alessandro Grippo Venice Beach Venice, Los Angeles, California CROSS BEDDING Cross Bedding Large scale cross beds © Alessandro Grippo San Juan County Utah, USA Cross Bedding Large scale cross beds from aeolian (wind) environment © Alessandro Grippo Checkerboard Mesa Zion National Park Utah, USA Cross Bedding a detail from the previous image © Alessandro Grippo Checkerboard Mesa Zion National Park Utah, USA Cross Bedding Large scale cross beds from aeolian (wind) environment © Alessandro Grippo The Wave Vermillion Cliffs Arizona, USA Cross Bedding Large scale cross beds, detail (width of image ca. 10 cm / 4 inches) © Alessandro Grippo Capitol Reef National Park Utah, USA Cross Bedding a side view of cross beds shows the basal contact with horizontal beds at the front of the structure (tabular cross bedding) © Alessandro Grippo Cadiz, California, USA Cross Bedding: a front view of cross beds shows curvy "packets" of beds (trough cross bedding) © Alessandro Grippo Cadiz, California, USA Cross Bedding: a lateral view of cross beds: climbing ripples within a Bouma sequence in turbidite deposits © Alessandro Grippo Palazzuolo sul Senio, Firenze, Italy RIPPLES (SYMMETRICAL and ASYMMETRICAL) Ripples wind-originated ripples in red (oxidized) sands (coin for scale) © Alessandro Grippo San Rafael desert Green River, Utah Ripples (asymmetrical ripples) these ripples form when water flows in one direction only © Alessandro Grippo Snake river Alpine Junction, Wyoming Ripples (symmetrical ripples) these ripples form when water flows back and forth © Alessandro Grippo Atlantic Ocean Nassau, Bahamas Ripples (symmetrical ripples) these ripples form when water flows back and forth © Alessandro Grippo Atlantic Ocean Nassau, Bahamas Ripples (symmetrical ripples) these ripples form when water flows back and forth © Alessandro Grippo Atlantic Ocean Nassau, Bahamas Ripples (symmetrical ripples) This sandstone shows evidence of an ancient beach © Alessandro Grippo Dakota Sandstone (Lower Cretaceous) Littleton Colorado, USA Ripples (asymmetrical ripples) formed by a receding tide: the ebb flow reshapes the sand © Alessandro Grippo Point Dume, California, USA Ripples: asymmetrical ripples formed by a receding tide: notice the steep side (downcurrent) and the gentle side (upcurrent); also notice the gravel collecting in the ripples' trough © unknown, from Flickr Indian Ocean, Bangladesh MUD CRACKS Ripples and Mud Cracks: asymmetrical ripples formed by wind action have been covered by water that deposited a thin veil of mud; desiccation of mud caused cracking and peeling (coin for scale) © Alessandro Grippo Canyonlands National Park, Utah, USA Mud Cracks with Raindrop Impressions desiccation caused mud to shrink and crack; raindrops left an impression on the polygonal surfaces (hammer for scale) © Andy Duncan Texas, USA Mud Cracks a desiccated thick mud layer originated very big and deep mud cracks (Jeep for scale) © Alessandro Grippo Lake Powell dry bed Hite Crossing Utah, USA Mud Cracks mud flows from a mud volcano often change direction. The abandoned flows quickly dry up and crack. (height of volcano: about 3 m, or 10 ft) © Alessandro Grippo Mud Volcanoes Field Nirano Modena, Italy Fossil Mud Cracks after desiccation, cracks were filled with sand and thus preserved (coin for scale) © Alessandro Grippo Glacier National Park Montana, USA GRADED BEDDING Turbidites: The lower part (a-b-c) of a Bouma sequence: the interval a is constituted by massive bedding; the interval b by parallel, horizontal lamination; the interval c by cross-bedding and convolute lamination. (coin for scale) © Alessandro Grippo Palazzuolo sul Senio, Firenze, Italy STROMATOLITES Living Stromatolites: algal mats trap sediment particles that force the algae to outgrow through them; layer after layer stromatolites are slowly built © Will Bakali Hamelin Pool, Shark Bay, Australia Fossil Stromatolites: notice the growth layers; stromatolites are useful both as environmental indicators (they require warm waters and absence of predators) and geopetal indicators © b. centley Helena, Montana, USA Fossil Stromatolites: these stromatolites are shown still embedded in surrounding sediment, thus providing a 3-D view of their structure (coin for scale) © Alessandro Grippo Glacier National Park, Montana, USA Fossil Stromatolites: a view from above of one of the stromatolites from the previous locality (coin for scale) © Alessandro Grippo Glacier National Park, Montana, USA Fossil Stromatolites: a cut-through section of one of the previous stromatolites, showing a characteristic mushroom-like shape (coin for scale) © Alessandro Grippo Glacier National Park, Montana, USA Fossil Stromatolites: a close-up detail of the previous stromatolite, showing details of the growth layers (coin for scale) © Alessandro Grippo Glacier National Park, Montana, USA Fossil Stromatolites: a view of a stromatolite patch along a road cut (vertical scale is about 5 m, or about 15 ft) (coin for scale) © Alessandro Grippo Glacier National Park, Montana, USA Fossil Stromatolites: a detail of the growth layers from the previous location (coin for scale) © Alessandro Grippo Glacier National Park, Montana, USA BIOTURBATION Bioturbation: biologic activity at the ocean bottom erases bedding; bioturbation is an indicator of optimal conditions for life, that is, abundance of oxygen © Alessandro Grippo Point Mugu, Ventura county, California, USA Bioturbation: a detail from the previous image © Alessandro Grippo Point Mugu, Ventura county, California, USA Bioturbation: another detail, with scale (purple pen for scale) © Alessandro Grippo Point Mugu, Ventura county, California, USA Bioturbation: Daemonhelix, or a "devil's corkscrew" (as exposed in a glass case at the National Park Visitor Center) © Alessandro Grippo Agate Fossil Beds National Monument, Nebraska, USA OTHER FEATURES Colored Parallel Beds: These alternating layers of limestone (whitish) and shale (reddish), from a core drilled in Cretaceous sediments, show continuously changing oxygen conditions at the bottom of the ocean at the time of their sedimentation (centimeter scale on the left) © Isabella Premoli Silva, Alessandro Grippo Piobbico core, Pesaro - Urbino, Italy Folds (tectonic structures): tectonic activity can cause folding of sedimentary layers; this picture shows why layers can be found upside down and geologists need a geopetal indicator © Stevie D - Earthwatcher Cornwall, England, United Kingdom Rock Colors Diagram: A diagram introducing to the relationships between lithologies and different oxygen conditions) © Alessandro Grippo modified from Alessandro Grippo et al., SEPM Special Publication volume 81, (2005) Tulsa, Oklahoma, USA all photos © Alessandro Grippo, except where indicated Back to Top | Back to Home Page © Alessandro Grippo, 1994-2010 Los Angeles, California